Lack of sleep could be bad for the character too. Look at Donald Trump | Letters

The less people sleep, the less they remember, the less they learn, the less they understand and the less they empathise

Too little sleep, like alcohol, tobacco, red meat, burnt toast and everything else, can kill us (Rachel Cooke, “‘Sleep should be prescribed’”, New Review). But beyond sleep and death, there is sleep and life. The sleep expert Prof Matthew Walker implies that lack of sleep can cause mental illness; he also says: “I get on a flight at 10am when people should be at peak alert, and I look around, and half of the plane has immediately fallen asleep.”

The less people sleep, the less they remember, the less they learn, the less they understand and the less they empathise. In the moralist’s terms, the less people sleep, the less capable they will be of having a conscience, feeling solidarity or possessing a decent character. At the same time, sacrificing sleep presumably correlates to advancement in business and politics and being an important person flying somewhere.